8 Acknowledgements

We acknowledge Nader Azarmi for encouraging us to write this paper, particularly through his provision of a fraction of the literature referenced in it. David Griffiths also encouraged the writing of this article. Several informal discussions with Barry Crabtree, Mark Wiegand, Paul OíBrien, Robin Smith and Nader Azarmi have also shaped some of the views propounded in it. Barry, Robin, Nader, Divine Ndumu and Brian Odgers have also provided feedback which has improved the quality of this paper. Lastly, we acknowledge the comments of the three anonymous reviewers, though two of them were not so anonymous afterall. The author bears all the responsibility for any misunderstandings and/or errors therein. The views expressed are also those of the author, and not necessarily those of BT plc. This work was funded by BT Laboratories.